Heat wave to have firm grip on northwestern US into end of July

By Kristina Pydynowski, AccuWeather senior meteorologist

July 22, 2018, 5:02:03 PM EDT

The remainder of July will be dominated by a resurgence of heat across the northwestern United States.

The recent reprieve from the mid-July heat wave in the Northwest has come to an end as the heat intensifying over the Southwest will also expand its grip northward.

"This stretch of heat actually looks to be longer than what was experienced in mid-July," AccuWeather Senior Meteorologist Dan Pydynowski said. "After returning on Sunday, the heat could last right through next weekend."

Highs are expected to soar 5-15 degrees above normal daily through the final full week of July. That will translate into highs near 90 F in Seattle; 90s in Portland, Oregon; around 100 in Pendleton, Oregon, and Boise, Idaho; and the lower 100s in Medford, Oregon.

"Even though humidity levels will remain relatively low through the heat wave, many in the Pacific Northwest do not have air conditioning, so the prolonged heat wave will be dangerous with day after day of sunny and hot conditions," Pydynowski said.

Higher humidity slows the rate at which the body can cool itself through sweat evaporating.

Residents are reminded to drink plenty of water, wear light-colored clothing and avoid strenuous activities during the midday and afternoon hours (the hottest times of the day).

Never leave a child or pet in sealed vehicle without air conditioning even for a short amount of time. Cars can become dangerously hot in only a matter of minutes. As of July 21, there has been 27 child hot car fatalities in the United States, according to KidsandCars.org.

Those seeking relief from the heat can head to the immediate coast, where more comfortable highs in the upper 60s and 70s will prevail.

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Fire crews battling the nearly two dozen wildfires burning across the Northwestshould also be encouraged to take the necessary precautions to avoid heat exhaustion or stroke.

As temperatures soar, trapped smoke from those blazes and pollutants can contribute to another hazard across the Northwest.

"Similar to what occurred in mid-July, the setup of calm, sunny and increasingly hot weather will again allow air quality to deteriorate throughout the coming week," AccuWeather Meteorologist and Air Quality Blogger Faith Eherts said.

"Anyone planning on spending time outdoors camping, hiking or otherwise exercising should stay up-to-date on local air quality alerts," Eherts said.

Poor air quality can force the elderly, children and those with respiratory issues to limit time spent outside.

Remain vigilant of cigarette butts and other sparks to avoid igniting new wildfires. The hot weather this week will only further dry out the vegetation across the region.

Spotty thunderstorms that develop over the higher terrain can do more harm than good by producing little rainfall, but lightning and gusty winds.

The concern for these dry thunderstorms is highest near the border of Oregon and California and into northern Nevada and extreme southern Idaho through at least midweek.

While the heat can be relentless through the final days of July, there may be relief after the calendar flips to August.

"The heat may get pushed back briefly during the first days of August," according to AccuWeather Long-Range Meteorologist Paul Pastelok.

Prior to that, this heat wave can enter record books.

The heat wave in mid-July led to six consecutive days of temperatures reaching or exceeding 90 in Portland.

If the current stretch of heat lasts through July 30, as anticipated, a new record for the most 90-degree days in July can be set. July 2009 holds the record with 14 such days registered at the city’s airport.

This heat wave may also produce a few daily record highs in other cities across the Northwest.

How hot do you think it’ll get? Make your prediction and play Forecaster Challenge.